Asian Journal of Medical Sciences 3(2): 74-78, 2011
ISSN: 2040-8773
© Maxwell Scientific Organization, 2011
Received: February 23, 2011
Accepted: March 26, 2011
Published: April 20, 2011
Anogenital Distance of Newborns and Causes of Variation in Zaria,
Northern Nigeria
1
O.M. Avidime, 1K.V. Olorunshola and 2A.A.U. Dikko
Department of Human Physiology, Faculty of Medicine, Ahmadu Bello University,
Zaria, Nigeria
2
Department of Human Physiology, Faculty of Medicine, Bayero University, Kano, Nigeria
1
Abstract: The aim of this study is to determine the anogenital distance in male and female newborns in Zaria
and possible causes of variation. The anogenital distance (AGD), serum testosterone and anthropometric
measurements of 200 newborns was measured (100 male, 100 female). Data obtained were analysed using
Student t-test, ANOVA and Pearson’s correlation as applicable. The mean total anogenital distance was
22.53±0.70 mm, (males: 31.11±0.64 mm and in females: 13.89±0.26 mm). Newborns of Igbo ethnicity had the
highest mean AGD of 32.77±1.63 mm (males) while the females had a mean anus to fourchette distance of
14.63±1.14 mm. There was significant positive correlation between anogenital distance and head circumference
in male newborns and birth weight in female newborns in the population examined (p<0.05). Testosterone
concentration, placenta weight, birthlength and birthorder did not correlate with Anogenital distance. It is
concluded that ethnicity, birth weight and head circumference significantly affect anogenital distance in the
population examined in Zaria, Nigeria.
Key words: Anogenital distance, anthropometric, ethnicity, umbilical cord testosterone
Measurement of AGD using a flexible ruler which
conformed to the natural curves of the perineum and
measurement under anesthesia improved accuracy by
eliminating any motion artefact. (Hsieh et al., 2008)
Some factors such as gestational age, ethnicity, race
and birth weight, intrauterine exposure to steroids and
endocrine disruptors are known to affect AGD
(Callegari et al., 1987; Phillip et al., 1996, SalazarMartinez et al., 2004). The major ethnic groups in Nigeria
are Hausa, Yoruba, Igbo and other minorities grouped
together as others
In Nigeria, there is extensive use of pesticides with
little or no regulation of its use, cosmetics, diet and
household items containing endocrine disrupting
chemicals with deleterious effects on reproductive and
endocrine homeostasis consequent on reproduction/
fertility (Olorunshola et al., 2009). To the best of our
knowledge, there is no report on AGD in newborns in
Nigeria, consequently, this study was designed to
determine the anogenital distance in Zaria and attempt to
determine possible causes of variation.
The aim of this study is to determine the anogenital
distance in newborns and possible causes of variation in
Zaria, Northern Nigeria.
INTRODUCTION
Anogenital distance (AGD) is the distance between
the anus and the base of the penis in males and anus to
fourchette (AF) distance in females and is a sexually
dimorphic index that, on average, is twice as great in
males as in females, and serves as a marker of proper
male development. (Callegari et al., 1987, SalazarMartinez et al., 2004; Weisse, 2006).
The utility of Anogenital Distance (AGD)
measurement in humans is supported by experimental
data in primates showing that in utero exposure of
females to androgenic agents increased AGD
(Hendrickx et al., 1987). The purported mechanism by
which androgens increase AGD in females is by inducing
"labioscrotal fusion" (in normal males fusion begins
caudally and proceeds ventrally, presumably androgens in
females act the same way) (Callegari et al., 1987).
Measuring the anogenital distance in neonatal
humans has been suggested as a non-invasive method to
predict neonatal and adult reproductive disorders such as
cryptorchidism and hypospadias (Hsieh et al., 2008).
Abnormal AGD is associated with premature breast
development in young girls (Colón et al., 2000).
Corresponding Author: Ohunene M. Avidime, Department of Human Physiology, Faculty of Medicine, Ahmadu Bello University,
Zaria, Nigeria. Tel: +2348037053285
74
Asian J. Med. Sci., 3(2): 74-78, 2011
parturients within 6 h of birth to obtain sociodemographic
details of mothers including family history and that of the
husband, history of drug intake, cigarette smoking,
alchohol consumption, obstetric history and ethnicity.
MATERIALS AND METHODS
Study design: This study is a cross sectional study
conducted in Zaria, Northern Nigeria between June and
August 2010. Questionnaires were used to obtain
pregnancy history. Measurement of birth weight, birth
length, head circumference and anogenital distance in
newborns from consenting parturients were recorded.
Anogenital distance measurement: The newborn infant
was kept in the dorsal decubitus position; with the aid of
an assistant, both hips were flexed and light pressure was
exerted on the newborn’s thighs until the assistant’s hand
touched the subject's abdomen. Measurements were made
with flexible tape. Distance was measured from the center
of the anus to the posterior convergence of the fourchette
(where the vestibule begins) in female infants and from
the center of the anus to the junction of the smooth
perineal skin with the rugated skin of the scrotum in male
infants.
Results were recorded in millimetres
(Callegari et al., 1987). Gestational age was estimated
according to the Dubowitz
scoring system
(Dubowitz et al., 1970).
Demography of study area: Zaria is a cosmopolitan city
in Kaduna State, Nigeria inhabited by about 408,198
people as stated by the 2006 census report
(Wikipedia, 2011). Different tribes and ethnic groups can
be found in Zaria, the three major ethnic groups: Hausa,
Yoruba, Igbo and minorities grouped together as others.
Zaria occupies a portion of the high plains of Northern
Nigeria, 652.6 m above sea level and some 950 km from
the coast at 11º04!N, 7º42!E. Zaria is the second largest
city in Kaduna State of Nigeria with many tertiary
institutions of learning and research including Ahmadu
Bello University Zaria.
The climate is Savannah with annual rainfall ranging
from 0.0 to 816.0 mm/month and minimum and maximum
temperature 15.3 and 36.25ºC, respectively.
Other anthropometric measurements were determined as
follows:
Birth weight: Without clothing the newborns were
weighed on a basinet weighing scale. Weight was taken
to the nearest 10 g (Athreya, 1980).
Ethical consideration: The study recruited paturients
only after detailed explanation as to the nature and benefit
of the study had been given, and verbal and or written
consent obtained
Approval for this study was obtained from the Ethical
Committee on Human Research of the Ahmadu Bello
University Teaching Hospital, Shika, Zaria, Nigeria.
Birth length: Birth length was measured in the supine
position, the feet were held against a fixed foot piece at
the 0 mark and a movable head piece was brought to
touch firmly against the vertex. The readings were
recorded to the nearest 1 cm (Athreya, 1980).
Study population: The study population used was
consecutive consenting paturients in labour at the
Ahmadu Bello University Teaching Hospital, Shika-Zaria,
Hajiya Gambo Sawaba General Hospital, Kofan Gayan,
Zaria, Major Ibrahim B. General Hospital, Sabon Gari,
Zaria and Salama Infirmary, Zaria
Head circumference: Head circumference was measured
using a non-stretchable tape over the maximum point of
occipital protuberance and above the the superior orbital
ridges anteriorly (Athreya, 1980).
Placenta weight: The placenta was tied in a polythene
bag and weighed on a basinet scale. Placenta weight was
taken to the nearest 10g (Athreya, 1980).
Exclusion criteria: Non-consenting parturients and
newborns with obvious anogenital anomalies such as
imperforate anus and ambiguous genitalia were excluded
from the study.
Statistical analysis: All data was recorded as mean ±
SEM and was subjected to statistical analysis using
Student t-test, Analysis of Variance and Pearson’s
Correlation test where applicable. A p value of equal to or
less than 0.05(p#0.05) was considered statistically
significant.
The Statistical Package for the Social Science (SPSS)
for Windows Version 17.0 was used for all calculations
and statistical analysis.
Subjects: A total of two hundred (200) newborns were
recruited for the study, the first one hundred male and first
one hundred female deliveries without any obvious
anogenital anomalies which took place within the period
of July and August 2010 in the aforementioned hospitals.
Following admission into the labour room, structured
questionnaires were administered to consenting
75
Asian J. Med. Sci., 3(2): 74-78, 2011
Table 1: Anogenital distance by ethnicity and sex
Mean±SEM
---------------------------------------------------------------------Tribe
Male
Female
Total
Hausa
31.38±0.88
13.85±0.31
24.07±1.03
Yoruba
27.50±1.92
13.43±0.61
17.65±1.63
Igbo
32.77±1.63
14.63±1.14
22.76±1.95
Others
30.52±1.30
13.77±0.36
21.38±1.29
Total
31.11±0.64
13.89±0.26
22.50±0.70
Table 4: Correlation matrix of AGD and testosterone, birth weight,
head circumference, birth length and placenta weight (n =
100) in males
Variables
TC
PW
AGD
HC
BL
BW
TC
1
-0.06
0.26
-0.09
0.14
0.08
0.23
0.53c
PW
1
0.07
0.45c
AGD
1
0.23a
0.04
0.15
HC
1
0.48c 0.56c
BL
1
0.43c
BW
1
TC: Testosterone Concentration; PW: Placenta Weight; AGD:
Anogenital Distance; HC: Head Circumference; BL: Birth Length; BW:
Birth Weight; a = p<0.05; b = p<0.01; c = p<0.001
Table 2: Mean anogenital distance, testosterone concentration, placenta
weight and some anthropometic measurements of newborns
Mean±SEM
---------------------------------------------------------------Male (n = 100) Female (n = 100) Total (n = 100)
AGD (mm)
31.11±0.64
13.89±0.26
22.50±0.70
T. Conc (ng/mL) 2.78±0.30
2.09±0.22
2.44±0.19
Placenta wt(kg)
0.88±0.26
0.69±0.02
0.78±0.10
Birth length (cm) 50.13±0.40
49.24±0.37
49.19±0.27
Head circum(cm) 34.45±0.21
34.23±0.21
34.34±0.15
Birth weight (kg) 3.23±0.06
3.04±0.05
3.03±0.04
and in females 34.23±0.21 cm, this was statistically
significant (p = 0.50) while mean birth weight was
3.23±0.06 kg in males and 3.04±0.05 kg in females was
also not statistically significant (p = 0.88).
Table 3 and 4 show correlation between the
parameters used, in femalesthere was positive correlation
between birth weight and anogenital distance, head
circumference and birth length and also positive
correlation between head circumference and birth length.
In males, there was positive correlation between head
circumference and anogenital distance, placenta weight,
birth length and birth weight, there was also positive
correlation between birth weight and placenta weight,
birthlength.
Table 3: Correlation matrix of AGD and testosterone, birth weight,
head circumference, birth length and placenta weight (n =
100) in females
Variables
TC
PW
AGD
HC
BL
BW
TC
1
0.12
-0.05
0.25
-0.09 0.27
PW
1
-0.01
0.04
0.20
0.11
AGD
1
0.17
0.10
0.23a
HC
1
0.382c 0.52c
BL
1
0.44c
BW
1
TC: Testosterone Concentration; PW: Placenta Weight; AGD:
Anogenital Distance; HC: Head Circumference; BL: Birth Length; BW:
Birth Weight; a = p<0.05; b = p<0.01; c = p<0.001
DISCUSSION
The anogenital distance examined in this population
showed that male values are higher than female values.
The report is not different from other investigations which
reported higher values for males (Salazar- Martinez et al.,
2004), this clearly shows the sexual dimorphism in males
and females (Weisse et al., 2006).
The mean anogenital distance in this study was 22.52
mm (males and females), higher than 18mm which was
obtained by Salazar- Martinez et al. (2004). Values
obtained by Salazar-Martinez et al. (2004) for males and
females were 21 and 11 mm, respectively. The SalazarMartinez et al. (2004) study was conducted in Morelos,
Mexico. In this study, values obtained were 31.11 mm in
males and the anus to fourchette (AF) distance was 13.89
mm in females, higher than the values obtained in the
study by Salazar-Martinez et al. (2004), this could
probably attributed to geographical differences and
environmental factors as reported by SalazarMartinez et al. (2004), while they had a mean birth weight
of 3.07 and 3.06 kg for males and females, respectively.
A total mean birth weight of 3.23 kg was obtained for
males and 3.04±0.56 kg for females was obtained in this
RESULTS
Anogenital Distance (AGD): Table 1 shows the mean
anogenital distance of the newborns of the different ethnic
groups used in this study. The total mean AGD of the
newborns was 22.50±0.70, 31.11±0.64 mm in males and
in females the total anus to fourchette distance was
13.89±0.26 mm.
Newborns of Igbo ethnicity had the highest mean
AGD; 32.77±1.63 mm in males and 14.63±1.14 mm in
females, while Yorubas had a mean AGD 27.50±1.92 in
males and 13.43±0.61 mm. Hausas had a mean AGD of
31.38±0.88mm in males and 13.85±0.31 mm in females.
There was no statististically significant difference
between Hausas and Yorubas (p>0.05)
Table 2 shows the mean of other parameters
measured. Mean birth length for male newborns was
50.13±0.40 cm, while in females 49.24±0.37 cm. There
was no statistical significance between them (p = 0.83).
Mean head circumference in males was 34.45±0.21 cm
76
Asian J. Med. Sci., 3(2): 74-78, 2011
study comparable to the values obtained by SalazarMartinez et al. (2004).
Other literature cited in this study did not separate the
newborns by weight classification. (Swan et al., 2005;
Salazar-Martinez et al., 2004; Phillip et al., 1996;
Callegari et al., 1987).
Callegari et al. (1987) used a mean birth weight of
2.53 kg. The mean anus to fourchette (AF) distance in
their study was 10.9 mm. Philips et al. (1996) used a birth
weight above 2.75 kg and they got an anus to fourchette
(AF) distance value of 16.1 mm in Jews and 16.5 mm in
Bedouins as compared to 13.89 mm in this study, which
is a lower value.
The highest value for AGD in males in this study was
44.00 mm in a newborn that weighed 2.20 kg while the
lowest was 17 mm in a newborn that weighed 1.45 kg.
Probably this shortened AGD could be attributed to the
low birth weight. It is also reported that phthalate
exposure in utero could lead to decreased AGD
(Barlow and Foster, 2003; Foster et al., 2000;
Hendrickx et al., 1987).
The highest anus to fourchette (AF) distance was 30
mm in a newborn that weighed 3.0 kg while the lowest
AF distance was 8.00 mm in a newborn weighing 2.0 kg.
This high AF distance value was obviously not related to
birth weight. It could have been as a result of chemical
exposure in utero as a result of cosmetic use or exposure
to pesticides, androgenic agents, etc., or diet as suggested
by Hauser (2005), Swan et al. (2005), Farr (2003) and
Hendrickx et al. (1987). The reduced AF distance may
also be related to diet (Tou et al., 1998. There was ethnic
difference in this study as in the investigation by
Philips et al. (1996). In the various ethnic groups in this
study, There was statistically significant difference in the
AGD between the different ethnic groups (p<0.05).
Hajiya Gambo Sawaba General Hospital, Kofan Gayan,
Zaria and Dr. Olugbenga Oguntunde for the statistical
analysis.
REFERENCES
Athreya, B.H., 1980. Clinical Methods in Pediatric
Diagnosis. Van Nostrand Reinhold Company,
Illustrated, ISBN: 0442233639, 9760442233631.
Barlow, N.J. and P.M. Foster, 2003. Pathogenesis of male
reproductive tract lesions from gestation through
adulthood following in utero exposure to Di(n-Butyl)
Phthalate. Toxicol. Pathol., 31: 397-410.
Callegari, C., S. Everett, M. Ross and J.A. Brasel, 1987.
Anogenital ratio: Measure of fetal virilization in
premature and full-term newborn infants. J. Pediatr.,
111: 240-243.
Colón, I., D. Caro, C.J. Bourdony and O. Rosario, 2000.
Identification of phthalate esters in the serum of
young puerto rican girls with premature breast
development. Environ. Health Perspect., 108: 895900.
Dubowitz, L.M., V. Dubowitz and C. Goldberg,
1970. Clinical assessment of gestational age in the
newborn infant. J. Pediatr., 77: 1-10.
Farr, G., 2003. Why you Should Avoid Soy-Link
Between High Soy Diet During Pregnancy and
Nursing and Eventual Developmental Changes in
Children.
Retrieved
from:
www.become
healthynow./articlecom@1700hrs. (Accessed on:
May 10, 2010).
Foster, P.M., R.C. Cattley and E. Mylchreest, 2000.
Effects of Di-n-Butyl Phthalate (DBP) on male
reproductive development in the rat: Implications for
human risk assessment. Food Chem. Toxicol., 38:
S97-S99.
Hauser, R. and A.M. Calafat, 2005. Phthalates and human
health. Occup. Environ. Med., 62(11): 806-818.
Hendrickx, A.G., R. Korte, F. Leuschner, B.W. Neumann,
S. Prahalada, A. Poggel, P.E. Binkerd and P. Gunzel,
1987. Embryotoxicity of sex steroidal hormone
combinations in non-human primates: I.
norethisterone acetate + ethinylestradiol and
progesterone + estradiol benzoate (Macaca mulatta,
Macaca fascicularis and Papio cynocephalus).
Teratology, 35: 119-127.
Hsieh, M.H., B. Breyer, M.L. Eisenberg and L.S. Baskin,
2008. Associations
among
hypospadias,
cryptorchidism, anogenital distance and endocrine
disruption. Curr. Urol. Rep., 9(2): 137-142.
CONCLUSION
We conclude that the anogenital distance in the
population studied is not different from that found in other
regions and AGD positively correlated with head
circumference in males and birth weight in females.
ACKNOWLEDGMENT
The authors acknowledge the assistance of the
Medical Director and staff of Salama Infirmiry, Zaria,
Nigeria, the tireless support of Dr. Solomon Avidime of
the Department of Obstetrics and Gynaecology, Ahmadu
Bello University Teaching Hospital, Zaria, Nigeria,
Maternity Wards of St. Luke’s Hospital, Wusasa, and
77
Asian J. Med. Sci., 3(2): 74-78, 2011
Tou, J.C.L., J. Chen and L.U. Thompson, 1998. Flaxseed
and its lignan precursor, secoisolariciresinol
diglycoside, affect pregnancy outcome and
reproductive development in rats. J. Nutr., 128: 18611868.
Weisse, B., 2006. Anogenital distance; defining ‘normal’.
Environ. Health Persp., 114(7): A399.
Wikipedia, 2011. The Free Encyclopedia. Retrieved from:
www.en.wikipedia.org/wiki/zaria.@14.14hrs.
(Accessed on: February 17, 2011).
Olorunshola, K.V., F.O. Akanbi and M.E. Ekanem, 2009.
Effect of cypermetrin (ripcord/cymbush) on thyroid
functions of albino rats. The Toxicologist, 108:
245-246.
Phillip, M., C. De Boer, D. Pilpel, M. Karplus and
S. Sofer, 1996. Clitoral and penile sizes of full term
newborns in two different ethnic groups. J. Pediatr.
Endocrinol. Metab., 9: 175-179.
Salazar-Martinez, E., P. Romano-Riquer, E. YanezMarquez, M.P. Longnecker and M. Hernandez-Avila,
2004. Anogenital distance in human male and female
newborns: A descriptive, cross-sectional study.
Environmental Health: A Global Access Science
Source, 3: 8.
Swan, S.H., K.M. Main, F. Liu, S.L. Stewart, R.L. Kruse,
A.M. Calafat, C.S. Mao, J.B. Redmond,
C.L. Ternand, S. Sullivan and J.L. Teague, 2005.
Decrease in anogenital distance among male infants
with prenatal phthalate exposure. Environ. Health
Perspect., 113: 1056-1061.
78